For the three boards you mentioned, as tile backer boards on their own, I prefer wonderboard over Hardi over Easy.

Behind Kerdi I'd take Wonder over Hardie as well. I can't comment as I've never used Kerdi over Easy, but I suppose it would work fine.

The only warning with Easy and steam showers is that the high temps of the steam nozzle can deform or melt the foam core of the Easy. Not a factor for you since you'd only use Easy on the ceilings.

Mongo

Schluter recommends using standard drywall. Kerdi is waterproof and NOTHING gets behind it. Why make more work for yourself?

Same argument I've given John and Cx every time it's come up. Condensation. And yes, I've heard their arguments against it, but I'm not convinced. Sorry, Laz. I think it's money well spent.

Having just finished much the same project, I used Hardibacker. Wonder-board weighs a ton & is hard to cut accurately. The venerable & all knowing masters who grace this forum must be relatively studly young men since even a full sheet of Hardibacker can get a bit heavy for an antique DIYer like myself. It would also help to have prehensile genitalia to hold the board while you install it.

With all due respect to the masters, let us talk about Kerdi which is a waterproofing product which you adhere to the wall with a water based material. That doesn't seem to make a lot of sense & guess what? It doesn't. Kerdi is a real PITA to install. The only way that It was finally installed was by skim coating the Hardi which wicks the moisture right out of the thinset. One would think that the Kerdi could be sized with a hydrophilic compound.
On my next bathroom I am going to use WEDI. The cost doesn't matter as the wear and tear on my body and tools as well as the extra time involved in installation would be prohibitive if I were to do it with the same set up. An old feeble geezer like myself has more money than time or health.

Like the Easy board, WEDI has a foam core. I plan on running a copper or brass sleeve around the pipes with some clearance to protect the foam.
WEDI also claims to be waterproof, & if that holds to be true, then there is no need for Kerdi. I sincerely apologize to the Masters, but I cannot give a "thumbs up" to the Kerdi and Wonder/Hardi combo. Been there, done that, no thank you very much.
Lastly I would never use Kerdi over drywall. as the drywall just isn't sturdy enough for the job & if the Kerdi installation is flawed or the kerdi develops a hole, you will have a disaster.

GOOD LUCK!